The present invention relates to a device for protecting a skin area against light when detecting and/or treating skin disorders, especially cancer and its preliminary stages, including application of compounds and/or compositions to the skin, in connection with which a photoreactive substance appears in the skin area.
Skin cancer may be detected optically by applying a gel, ointment or the like containing deltaaminolevulinic acid (ALA) to the skin area and letting this mixture act on the skin from 1 to 24 h, after which the ALA mixture is removed. In the skin, ALA is transformed into protoporphyrin IX. When the ALA substance has been allowed to act on the skin, protoporphyrin IX has formed in greater quantities in those parts of the skin area where there is a skin disorder than in the rest of the skin area. Then the skin area is illuminated by light of a certain wavelength and intensity. Protoporphyrin IX has such properties that those parts of the skin area which have a skin disorder and thus contain a particularly high concentration of the substance, will fluoresce with higher intensity than the other parts of the skin area. The fluorescence is registered by means of a camera and is evaluated. In order to obtain good and reliable results, the radiation needs a certain wavelength, and the chamber which catches the fluorescent radiation must also have the requisite filters so that only light of a certain wavelength will be registered. ALA, which is easily soluble in water, is applied in an oil-in-water or water-in-oil form or as a gel. Usually, a nurse applies ALA to the patients to be examined, but the patients themselves may also apply ALA at home and bandage up the site of application, and then after a few hours they go to the hospital for detecting of cancer. This whole cancer detection method is described in Swedish patent 9603095-2.
By using ALA, it is also possible to directly attack the changed skin cells, for example cancer cells, by special light treatment of the skin area, which gives rise to phototoxic reactions originating from protoporphyrin IX.
Whether such treatment takes place or not, the skin is sensitive to light after the removal of superfluous gel, even some time after the detection procedure.
The purpose of applying compounds or compositions comprising ALA is thus to prepare the skin area for subsequent detection of skin disorders, especially cancer and its preliminary stages, by means of fluorescent light and/or to treat the area with light, a phototoxic reaction taking place which is injurious to the changed cells, for instance cancer cells.
The very application itself of compounds and/or compositions, such as ALA, to the skin in the above-described manner is easy and causes no problems. However, there is a difficulty since light has to be shut out from the skin area to which compounds and/or compositions have been applied so that no unwanted photoreactions will take place. These unwanted phototoxic reactions result in uncontrolled treatment and bleaching and may take place both before and after the detection procedure. It is also important that the compounds and/or compositions are applied in correct quantities and that the skin area is not disturbed during or after the treatment with compounds and compositions.
Solution
The present invention has thus solved the above problem in protection of the area at issue against light and provided a device for protecting a skin area against light in connection with detection or treatment of skin disorders including application of compounds and/or compositions to the skin, in connection with which a photoreactive substance appears in the skin area, the device being characterised in that it comprises an opaque foil forming a cavity relative to the skin and having edges engaging the skin, the width of the edges being determined by the formula:   m   greater than       δ    ·          ln      ⁢              (                              t            ·                          I              0                                            D            diffused                          )            
wherein
m=the width of the edge,
xcex4=the penetration depth of the light in the skin,
ln=the natural logarithm,
t=the time of the effect of the light,
I0=the luminous intensity at the skin surface, and
Ddiffused=the diffused energy dose which is allowed to reach the skin area to which ALA is applied.
Such a device limits the dose of photoactivating luminous energy that is diffused under the edges and into the area of treatment. The frequent light which has the greatest penetration depth is to be found in the red area of the visible spectrum and may, for example, have a wavelength of 600-650 nm.
It is suitable that the diffused energy dose is below, for example, 0.2 J/cm2 to prevent an unwanted photoactive effect on the skin. The width of the edges may then be 10-20 mm.
Preferably, the photoreactive substance can be protoporphyrin IX, the properties of which are relatively well known.
Conveniently, compounds and/or compositions containing deltaaminolevulinic acid (ALA) may be applied to the skin.
An example of compositions comprising ALA is a cream or a gel which contains an ALA compound. Another example is deltaaminolevulinic acid itself.
According to the invention, it is suitable that the foil is formable and consists of metal, metal on plastic or opaque plastic. It is also advantageous if the foil is made of a heat-insulating material, for example metal foil. This gives a higher temperature in the skin area concerned, which results in a better blood supply, and thus oxygen supply to the same. Since oxygen is essential for the phototoxic effect used for the detection, such a plaster contributes to the efficiency of the treatment. The higher temperature also has a favourable effect on the formation of protoporphyrin IX.
Such a device can be used as an application and protection device for applying compositions and/or compounds to the skin, and protecting the area at issue against sunlight before and after the detection procedure.
When the device is intended to be used for the application of a certain substance, i.e. a composition and/or compounds in connection with which a photoreactive substance appears on the skin before detection and an optional treatment, the cavity formed relative to the skin preferably contains the substance to be applied to the skin. The fact that the application takes place in this way ensures that no substance will get outside of the desired area, for instance, under the edges of the device or completely outside of the device. Such a misplaced substance would be more or less unprotected against light and might then cause skin injuries.